As concern for global environment problems and energy problems increases, in recent years the Energy Star program, for example, generally requires the saving of energy in various apparatus. This also applies to communication apparatus. A reduction in the power consumption of communication apparatus is required.
If a link transmission speed is once determined in a communication system such as a wired LAN (Local Area Network), usually the link transmission speed is kept as the amount of packets in a network. This link transmission speed is maintained unless a user himself/herself changes it.
Japanese Laid-open Patent Publication No. 2006-304241
Japanese Laid-open Patent Publication No. 2006-270470
In a wired LAN, for example, the power consumption of a LAN chip in 1000BASE-T in which a transmission speed is high may be at least twice that of a LAN chip in 100BASE-TX in which a transmission speed is low. Accordingly, if communication is always performed in such a communication system, it is necessary to keep a state in which high-speed communication that leads to high power consumption can be performed. However, communication (and data communication itself) the quality of which is guaranteed is not always performed in a network. This is an unnecessary waste of power and is not desirable from the viewpoint of the saving of energy.